Performance of sustainable hybrid self-compacting concrete with glass powder and alkali-activated fly ash
ABSTRACT This study investigates the fresh, mechanical, durability, and microstructural performance of self-compacting concrete (SCC) incorporating alkali-activated fly ash (FFA), glass powder (GGP), and their hybrid combinations with ordinary cement (OC). The aim is to evaluate the feasibility of sustainable SCC systems under low-molarity NaOH activation (1 M) while maintaining structural performance requirements. Results show that hybrid SCC mixtures achieved slump flow values between 495–640 mm, with T50 times ranging from 0.8 to 3.6 s, indicating acceptable flowability and stability. The 50OC–50FFA mixture exhibited a compressive strength reduction of 10–18%, while the 50OC–50GGP system showed a higher reduction of 15–25% compared to conventional SCC (100OC). Chloride ion permeability increased by 35–50% in 100FFA, whereas hybrid systems showed improved resistance with intermediate charge values, maintaining structural durability requirements. Freeze–thaw testing revealed durability factors exceeding 100% retention for hybrid mixes, while 100FFA failed after approximately 75 cycles. SEM and FTIR analyses confirmed that FFA promotes a denser geopolymeric network, whereas GGP exhibits limited reactivity under low alkalinity, behaving primarily as a filler. The study demonstrates that hybrid SCC systems provide a balanced trade-off between sustainability and performance, while also highlighting the limitations of low-alkali fly ash activation. Overall, the findings support the development of environmentally efficient SCC systems with improved durability and acceptable mechanical properties.